A splash screen is a graphical control element consisting of a window containing an image, a logo, and the current version of the software. A splash screen usually appears while a game or program is launching. A splash page is an introduction page on a website. A splash screen may cover the entire screen or web page, or may simply be a rectangle near the center of the screen or page. The splash screens of operating systems and some applications that expect to be run in full-screen usually cover the entire screen. (Wikipedia)
Splash screens are typically used by particularly large applications to notify the user that the program is in the process of loading. They provide feedback that a lengthy process is underway. Occasionally, a progress bar within the splash screen indicates the loading progress. A splash screen disappears when the application's main window appears.